The present invention relates to an analysis device for determining the relative percentages of various components within a mixture which includes at least two components having different electrical conductivities. More particularly, the invention concerns analysis devices of the type including at least two electrodes of different polarities which are connectable across an a.c. source, wherein the mixture is introduced between the electrodes for analysis. The present invention also relates to a method employing a device for analysis of a mixture.
The control and monitoring of industrial processes utilizing mixtures of at least two components having different electrical conductivities, requires devices capable of determining the relative percentages, concentration and/or density of the different components. These devices can also be required for processes which utilize components in the same or different physical states. Such a determination can be accomplished in a known manner with devices which ascertain and evaluate the data on the electrical conductivity or the relative dielectric constant of a mixture.
An apparatus that can be employed for this purpose is disclosed in Dechene et al U.S. Pat. No. 4,074,184. The device described therein includes six capacitor electrodes disposed about the circumference of a tube in a mutually circumferentially offset arrangement. A special electrical circuit charges the electrodes from a single-phase high frequency voltage source. This apparatus measures the capacitance of a mixture flowing through a tube and is therefore limited to analysis of components of electrically non-conductive materials.
A further example is found in Dechene et al U.S. Pat. No. 4,063,153. This patent describes an apparatus composed of three pairs of elongate electrodes arranged about the circumference of a tube. The mixture, whose component percentages are to be determined, is guided through the tube between the pairs of electrodes. An electrical circuit is utilized to measure the electrical resistance of the mixture between the electrodes. The electrodes must be in electrical contact with the conductive mixture. Thus, this apparatus is used to measure the electrical conductivity of a mixture. In many cases this leads to unsatisfactory measuring results since the conductivity of a mixture may fluctuate within wide limits. For example, in a mixture of water and air, the air has a substantially lower conductivity than the water. If the mixing ratio varies between 0 and 100% air, the resolution of an electrical circuit for evaluation of the measured values must be sufficiently high so that it is able to measure the high conductivity of the water for a water content of about 100% as well as the low conductivity of the air for an air content of about 100%. Such a requirement cannot be met in a manner that is technologically practical or economical.